The present invention relates to a driver circuit for driving current for use by a device such as an indicator lamp. In particular, the driver circuit is self-biased to permit driving an output current when supply voltage to the circuit is off.
In a safety system such as an airbag for an automobile, it is desirable to provide an indicator lamp to signal when a problem exists with the safety system. Typically, a circuit with control logic will light the indicator lamp when a problem is detected. Unfortunately, such a circuit generally performs only if a supply voltage is being applied to the driver circuit itself.